1. Field of the Invention
The present invention relates to a sensitivity adjustment device. More specifically, the present invention relates to an automatic sensitivity adjustment based on A/D conversion output data.
Priority is claimed on Japanese Patent Application No. 2012-205923, filed Sep. 19, 2012, the content of which is incorporated herein by reference.
2. Description of the Related Art
All patents, patent applications, patent publications, scientific articles, and the like, which will hereinafter be cited or identified in the present application, will hereby be incorporated by reference in their entirety in order to describe more fully the state of the art to which the present invention pertains.
For example, in a field device that is mounted on an installation site such as a piping passage of a plant in a process control system, as a switch mechanism that is manually operated by an operator setting parameters or the like at the site, there are mechanisms in which an infrared touch switch is incorporated.
FIG. 9 is an illustrative diagram of a constitution illustrating an example of an infrared touch switch of the related art in which a sensitivity adjustment function is incorporated. In FIG. 9, a light emitting unit 1 includes an infrared light emitting element. The infrared light emitting element is driven via a light emitting controller 4 based on a predetermined timing pulse signal which is generated and output by a timing controller 3 controlled by a CPU 2, and radiates outside of the facility.
For example, the light radiated from the light emitting unit 1 is reflected by a reflector 5 such as fingers of an operator, is incident on a light receiver 6, and is converted into analog electrical signals.
The analog electrical signals converted by the light receiver 6 are input to an A/D converter 7 which is controlled by the CPU 2, and are converted into digital signals.
The digital signals, which are converted and output by the A/D converter 7, are stored as touch detection data in a data storage region of a RAM 8 which is controlled by the CPU 2.
The CPU 2 performs overall control on the entire device based on a predetermined software program stored in a ROM 9, variable parameters appropriately set and stored in the RAM 8, or the like so that the device is operated as an infrared touch switch having a predetermined touch detection sensitivity.
A display unit 10 displays a predetermined display screen such as a process value display screen or a parameter setting screen which is created by a display controller 11 controlled by the CPU 2.
A nonvolatile memory 12 stores and holds sensitivity adjustment parameters for adjusting the touch detection sensitivity of the infrared touch switch via a nonvolatile memory controller 13 which is controlled by the CPU 2.
Based on the control of a communication controller 15 which is controlled by the CPU 2, a communication unit 14 executes transmission and reception of sensitivity adjustment parameters of the infrared touch switch between a communication tool (not shown) outside the facility and the communication unit 14.
Based on the control of the CPU 2, a switch operation determination unit 16 determines whether a touch detection operation is performed based on touch detection data converted and output by the A/D converter 7.
Operations of main units will be described in detail with reference to the drawings.
FIGS. 10(A) to 10(C) are illustrative diagrams of data sampling in the A/D converter 7 of the analog electric signals which are converted by the light receiver 6. In FIG. 10(A), a light emission pulse which is radiated from the light emitting unit 1, and is emitted and output based on a predetermined timing pulse signal which is generated and output by the timing controller 3 controlled by the CPU 2, is illustrated.
In FIG. 10(B), output data of the A/D converter 7 based on reflected light incident on the light receiver 6 is illustrated, and an A/D conversion operation of the A/D converter 7 is executed based on a predetermined sampling clock which is indicated by FIG. 10(C), and is generated and output by the timing controller 3.
Here, intensity of the reflected light is changed according to presence or absence of the reflector 5 or a difference of reflectance of the reflector 5, and a signal level of the output data of the A/D converter 7 is changed according to the change of the intensity of the reflected light. Moreover, the frequency of the light emission pulse or the timing of light-receiving A/D sampling may be arbitrarily determined. A signal level is used to mean a voltage level of a digital signal.
FIGS. 11A and 11B are illustrative diagrams of a threshold value which determines whether the touch detection operation is performed at the switch operation determination unit 16, and for example, is used for a comparison value of a signal level of output data of the A/D converter 7 at timings of t1 and t3 of the sampling clock of FIG. 10(C). FIG. 11A shows a state in which the signal level of the output data of the A/D converter 7 is less than the threshold value and a switch is determined to be “OFF.” FIG. 11B shows a state in which the signal level of the output data of the A/D converter 7 is equal to or more than the threshold value and a switch is determined to be “ON.”
The threshold value is set and input as a numerical value via the communication tool, and is stored and held in the nonvolatile memory 12 via the nonvolatile memory controller 13.
Circuit errors of the infrared touch switch or hardware characteristics including characteristics of the light emitting and light receiving elements, temperature characteristics, or the like are different individually, and thus the storage and holding of the threshold value are performed based on the fact that the individual threshold value is required for each switch.
Moreover, since the threshold value may be changed according to an adjustment examination in a manufacturing process via the communication tool or a setting of a user, it is necessary to store the threshold value in the nonvolatile memory 12.
FIGS. 12(a) to 12(e) are illustrative diagrams of a determination sequence in the switch operation determination unit 16. FIG. 12(a) shows an initial state, in which the switch is in an OFF state, and the A/D output is less than an A/D threshold value.
FIG. 12(b) shows a state in which the A/D output is changed from the state shown in FIG. 12(a) to a range in which the A/D output does not exceed the A/D threshold value. Since the A/D output is less than the A/D threshold value, the switch remains in an OFF state.
FIG. 12(c) shows a state in which the A/D output is increased from the state of FIG. 12(b) to a range in which the A/D output exceeds the A/D threshold value. Since the A/D output is equal to or more than the A/D threshold value, the switch is changed to remains in the ON state.
FIG. 12(e) shows a state in which the A/D output is decreased from the state of FIG. 12(d) to a range in which the A/D output is lower than the A/D threshold value. Since the A/D output is less than the A/D threshold value, the switch is changed to an OFF state.
FIGS. 13A to 13C are illustrative diagrams of sensitivity when there are differences in the hardware characteristics of the above-described infrared touch switch. FIG. 13A is an example of a high sensitivity switch, and shows a state in which the A/D output exceeds the A/D threshold value regardless of presence or absence of the reflector 5. In this case, the switch operation determination unit 16 responds regardless of the presence or absence of the reflector 5 and determines the switch is in the ON state, and the switch does not function as the infrared touch switch.
FIG. 13B shows an example of a medium sensitivity switch, and shows a state in which the A/D output is lower than the A/D threshold value when the reflector 5 is not present and the A/D output exceeds the A/D threshold value when the reflector 5 is present. In this case, the switch operation determination unit 16 does not respond when the reflector 5 is not present and determines the switch is in the OFF state, and responds when the reflector 5 is present and determines the switch is in the ON state, and thus the switch functions as the infrared touch switch.
FIG. 13C shows an example of a low sensitivity switch, and shows a state in which the A/D output is lower than the A/D threshold value regardless of the presence or absence of the reflector 5. In this case, the switch operation determination unit 16 does not respond regardless of the presence or absence of the reflector 5 and determines the switch is in the OFF state, and similar to that of FIG. 13A, the switch does not function as the infrared touch switch.
As is clear from FIGS. 13A to 13C, since the A/D output is largely changed according to the hardware characteristics of the infrared touch switch, it may be necessary to set the A/D threshold value to an optimal value such as an intermediate value between when the reflector is not present and when the reflector is present. Accordingly, the adjustment examination becomes essential in the manufacturing process.
FIGS. 14A to 14D are illustrative diagrams of sensitivity when there are differences in reflection characteristics of the reflector 5. FIG. 14A is an example when the reflector 5 is not present, the A/D output is lower than the A/D threshold value, and the switch operation determination unit 16 does not respond and determines the switch is in the OFF state.
FIG. 14B shows an example when the reflectance of the reflector 5 is low, the A/D output is lower than the A/D threshold value, and the switch operation determination unit 16 does not respond and determines the switch is in the OFF state.
FIG. 14C is an example when the reflectance of the reflector 5 is approximately intermediate, the A/D output exceeds the A/D threshold value, and the switch operation determination unit 16 responds and determines the switch is in the ON state.
FIG. 14D is an example when the reflectance of the reflector 5 is high, the A/D output exceeds the A/D threshold value, and the switch operation determination unit 16 responds and determines if the switch is in the ON state.
As is obvious from FIGS. 14A to 14D, the A/D output is largely changed according to flesh color of the fingers which are the reflector 5, color or stain of gloves, or the like. For example, in the case of the reflector 5 having low reflectance such as stained gloves, there is a concern that the switch may not respond as the infrared touch switch.
Moreover, when the switch is configured so that the user arbitrarily changes the threshold value, there is also a problem that touch detection distance of the infrared touch switch is largely different depending on the reflector.
Japanese Unexamined Patent Application, First Publication No. H9-270689 discloses a technology of a touch key which receives infrared light reflected by a reflector, detects the presence or absence of the reflector, and outputs key input signals.
According to the constitution of the infrared touch switch of the related art, a setting means according to the communication tool and a holding means to the nonvolatile memory are needed with respect to the sensitivity adjustment parameters.
Moreover, since the infrared touch switch is influenced by errors of the circuit configuring the infrared touch switch, various characteristics of the light emitting and light receiving elements, temperature characteristics, or the like, sensitivity adjustment means or sensitivity adjustment man-hours of the infrared touch switch are needed in the manufacturing process.
Moreover, since the infrared touch switch is influenced by the difference of the reflectance of the reflector, a sensitivity adjustment means or sensitivity adjustment man-hours of the infrared touch switch which are performed by the user are needed.
Furthermore, if the sensitivity adjustment parameters of the infrared touch switch are not appropriately adjusted, the operation of the infrared touch switch may be disabled.
Moreover, when the sensitivity adjustment parameters of the infrared touch switch are not appropriately set to be adjusted, there is a concern that operational feeling for each switch may be different.